The present invention relates to yarn finish formulations applied to yarns in order to facilitate the processing of yarns, for example, the winding of yarns and the knitting and weaving of yarns into fabric. More particularly, this invention relates to yarn finish formulations containing a viscosity index improver such as a polymethacrylate, a polyalkylstyrene, an ethylene propylene copolymer or a polyisobutylene, which provides better adherence to the fiber substrate, less propensity for dripping, less finish "throw-off" during high speed winding and the like properties due to an increase in the film strength of the finish formulation at high speed winding. This invention has special reference to synthetic yarns, for example, polyester, nylon and acrylic yarns, and is described in its exemplifications with respect thereto.
Yarn finishes, which are usually multicomponent mixtures of ingredients carried in a liquid base, are applied to yarns for a number of reasons. Synthetic yarns without a finish surface coating usually cannot be processed at high speeds, are prone to break during processing, may develop static charges and often exhibit unwanted high friction levels across machinery guides and the like. Thus, a plethora of ingredients are routinely admixed and applied to the yarn surface. Antistatic agents, lubricants, emulsifiers, thickening agents, among others, are usually included in finish formulations. However, certain problems persist in the art to which the present application, as will be apparent hereinbelow, is directed.
In certain fiber processing applications, it has become highly desirable, if not necessary, to provide a finish formulation for coating yarn which is highly adherent while presenting a low friction surface on the yarn. Anti-static protection for the yarn, generally, is also needed.
In the area of yarn coning oils, particular problems are presented which are not satisfactorily dealt with by commercially available products. Coning oils are lubricants applied after yarn texturing to impart desirable properties to the yarn when subsequently handled during rewinding and by the yarn knitter or weaver. Typically, coning oils comprise blends of a base lubricant with a major proportion of an inert carrier liquid, most often mineral oil.
The base lubricant (often a blend of two or more ingredients) used in coning oils, as well as in other yarn finishes containing lubricants, should have certain properties, namely (of course, the coning oil itself should also exhibit these properties):
(1) Lubricity: a lubricant is needed which reduces the coefficient of friction between fiber-to-metal surfaces in order to prevent fiber abrasion and maintain low, uniform tension during processing;
(2) Anti-static Control: a lubricant must have an anti-static property in order to dissipate static electric charges built up during processing;
(3) Cohesion: a balanced degree of cohesion is essential since too much lubricity can cause fiber slippage resulting in package distortion in winding and other operations;
(4) Oxidation Resistance: after lubricants are applied, the fibers are often stored for prolonged periods of time; therefore, lubricants must be resistant to discoloration, bacterial growth, and formation of insoluble resinous compounds in the presence of oxygen;
(5) Scourability: since poor scourability can cause dyeing problems and potential soiling spots, lubricants must come off the yarn under mild scouring conditions and for this reason it is desirable to have a self-emulsifiable type of lubricant;
(6) Controlled Viscosity Range: too low a viscosity causes difficulties in slinging of the finish off of the yarn and low yarn frictional values while too high a viscosity causes excessive finish add-on coupled with high frictional values;
(7) Non-allergenic and Non-toxic: a lubricant must not cause any dermatological reaction since mill workers, especially at the throwster level, are constantly exposed to the neat oil, as well as finished cones of textured yarn;
(8) Odor-resistance: since yarn is often stored for relatively long periods of time, odor formation is undesirable and often intolerable;
(9) Product Stability: since mills store lubricants for long periods before use, product separation is extremely dangerous since it can go unnoticed until several thousand pounds of yarn have been treated;
(10) Corrosion Resistance: the yarn comes into contact with many metal surfaces during processing, and rusting tendencies would be detrimental to expensive machine parts; also, yarn pickup of rust deposits would cause dyeing problems;
(11) Non-volatility: product volatilization causes a percentage loss of lubricant on the yarn which results in serious knitting problems;
(12) Color: the lubricant should be water-white and non-yellowing during processing or storage of yarns, for example, at temperatures used during yarn and/or fabric stabilization and dyeing;
(13) Emulsifiable: non-uniform, unstable and difficult to emulsify lubricants perform poorly in coning oil applications, for example, in causing variable effects during winding, scouring, dyeing and the like; and
(14) Adherency: the coning oil must not be thrown off of the yarn during high speed winding operations (termed "low slinging" in the art). This problem of "sling off" is exaggerated at points along the winding path where the yarn changes direction, for example, at traverse.
Of the above listing of desirable coning oil properties, providing a finish of controlled viscosity range in relationship to low slinging propensity at acceptable frictional values has presented a perplexing problem to the industry. For example, increasing viscosity through addition of high viscosity mineral oils or heavy metal soap gelling agents, such as aluminum stearate, deleteriously affects friction level and does not provide an oil of acceptable viscosity index characteristics (viscosity index refers to thinning (lowering of viscosity) under high temperature by high frictional shear condition).
Another area presenting particularly sensitive problems regarding adherence and friction level is that of needle oils used during knitting operations. Needle oils are conventionally applied as a spray to a plurality of steel knitting needles with the objective of lubricating the needles during the knitting operation. Obviously, a highly viscous lubricant characterized by high film strength and excellent adherence to the knitting needles is needed, along with superior frictional wear protection properties and at least adequate anti-static protection to reduce charge buildup around the knitting machine. Another prime requirement is resistance to fogging during spraying. Thus, if the finish does not essentially remain on the needles in the form of a continuous lubricating film, poor lubrication and needle wear will result. Further, finish will accumulate on and around other machinery parts, presenting hazardous working conditions and difficult clean-up tasks. Obviously, some needle oil will accumulate on the knitted fabric during processing so as an additional requirement the finish must be able to be washed from the fabric during the customary scouring and/or finishing operation to which fabrics are subjected. In essence, this means water washability. As stated above with respect to coning oils, a good viscosity index is needed to prevent thinning out of the needle oil when contacted by the hot, moving knitting needles.
In order to formulate coning oils, needle lubricants and similar finishes of high film strength and fiber adherence, as well as acceptable viscosity index characteristics, it has been thought that one need only use thicker fluid solvents, perhaps in conjunction with boundary lubricants. White oil has become the accepted coning and needle oil finish base, often providing 80 percent or more by weight of the finish formulation. However, it has been found that when one employs higher viscosity white oils to thicken a coning coil, other factors remaining constant, yarn-to-metal friction increases to unacceptable values at the high yarn speeds used today in the fabric formation and yarn winding arts. Also in the case of needle oils, the high viscosity oils thin out appreciably on heating and then lose their film strength and lubricating efficiency. As stated above, the use of heavy metal soap gelling agents does not satisfactorily solve these problems.
It has been found that the addition of a small amount by weight of a hydrocarbon soluble, long molecular chain polymeric viscosity index improver to an otherwise conventional finish formulation (the polymeric material being soluble and/or dispersable in the finish formulation) increases the viscosity of the formulation without altering the anti-friction attributes of the finish, particularly as to fiber/metal friction, even during high speed yarn processing. This finding is the subject of copending application U.S. Ser. No. 692,076, filed June 2, 1976, wherein the viscosity index improver is disclosed as a polymethacrylate, a polyalkystyrene, an ethylene-propylene copolymer or a polyisobutylene. It was believed that the higher viscosity of the finish resulted in better adherence to the fiber substrate, less propensity for dripping, less finish "throw-off" during high speed winding and the like properties due to an increase in film strength of the finish formulation at high viscosity.
It has also been found that it is not necessary to raise the viscosity of conventional finish formulations in order to increase film strength and adherence to the fiber substrate, and in turn develop less propensity for dripping, less finish "throw-off" during high speed winding and like properties. One may employ a yarn finish formulation having a viscosity below that conventionally desired, raise the viscosity of the finish to the normally desired level by the addition of a long molecular chain polymeric viscosity index improver and thereby obtain the above-noted improvements. One can select a mineral oil formulation having a viscosity below that normally employed for the particular processing and raise the viscosity thereof to the value of the finish normally employed by the addition of the viscosity index improver or the yarn finish may be derived from a blend of a mineral oil having a viscosity conventionally desired and a mineral oil having a viscosity below that conventionally desired and raising the viscosity of the blend to conventional levels with a viscosity index improver. These findings are the subject of copending U.S. application Ser. No. 675,421, filed Apr. 9, 1976.